This drop in filter has been available for a while.
I installed it right after I had the Bmw PPK installed, so cannot comment on any gains but I guess no one really expects much gains, if any, from a drop in anyway.
Regarding the sound, under wot almost no change at all, contrary to what I expected.
Only a barely noticeable sound change with partial throttle around 2.000 - 4.000 rpms.
If anyone is thinking to buy it hoping for a better sound, I would recommend not to.